POLYMORPHISM OF ACID AND NEUTRAL ALPHA-GLUCOSIDASES IN BANANA PULP - CHANGES IN APPARENT PIS AND AFFINITY TO CON-A OF THE ENZYMES DURING RIPENING

We observed the presence of acid and neutral alpha-glucosidases with optimum pHs of 4.5 and 6.5, respectively, and their multiple forms in banana pulp. By chromatofocusing analysis, each alpha-glucosidase from preclimacteric bananas was found to be of pI > 7.4, which disappeared upon ripening, although another form with pI 5 as a major component appeared instead. It is unknown whether this phenomenon is due to protein de novo synthesis and/or post-translational modifications of the enzyme. A large amount of acid alpha-glucosidase from preclimacteric bananas was shown to be a glycoprotein that bound to a Con A-Sepharose column. While this type of enzyme decreased during ripening, it remained a possibility that sugar components of the enzyme might be processed during ripening. The neutral alpha-glucosidase had no affinity to the column through ripening. These results provide preliminary information on the mechanism of appearance of alpha-glucosidase multiforms as well as on a useful strategy for purification of acid and neutral alpha-glucosidases from banana pulp at various stages of ripening.